Ink jet recording systems include methods employing respectively various types of ink such as water-based ink, oil-based ink, solvent ink and UV curable ink.
The ink jet recording systems which are of a curable type for actinic radiation such as ultraviolet radiation and EB have been attracting public attention recently, as a method to form images even on a base material having poor ink absorbency. These ink jet recording systems include a solvent type wherein a reactive monomer is diluted with water, water-based solvent or with various organic solvents, and a non-solvent type wherein no solvent remains after hardening. In recent years, non-solvent type ink is attracting public attention with a background in which non-VOC is desired.
As actinic radiation curable type ink which is cured by actinic radiation, there are known radically polymerizable ink composed mainly of an acrylate monomer and cationic polymerization ink composed mainly of an epoxy monomer or an oxetane monomer.
With respect to water-based ink, oil-based ink and solvent ink, many ink bags have been put to practical use, and there have been known structures wherein sufficient durability and storage stability are kept even when using the aforesaid ink.
However, an acrylate monomer, an epoxy monomer and an oxetane monomer which are used for actinic radiation curable type ink show properties which are greatly different from those of dilution solvent used for conventional water-based ink, oil-based ink and solvent ink, resulting in many problems especially in durability and storage stability for a long time, regarding storage of ink. The monomers have properties which are similar to those of plasticizers used as additives for plastic, and the monomers are easily soluble mutually with various plastics. Therefore, if the member which has been used is employed as a member that comes in contact with these ink, it degenerates with actinic radiation curable type ink because it has no ink resistance property, and its functions cannot be exhibited.
Compared with conventional dilution solvents, these monomer components tend to dissolve and swell remarkably the constituting members used for ink bags, which has caused a problem of deformation of ink bags. It has further been found that problems that an ink-jet nozzle is clogged, and that hardening sensitivities by actinic radiation are lowered, are caused, depending on the eluted components. In particular, cationic polymerization ink employing an epoxy monomer, an oxetane monomer or a vinyl ether monomer has caused problems that the ink erodes and swells various plastic members greatly and changes their dimensions and hardness, although the ink has advantages in terms of offensive smells, sensitivities and adhesion properties for a base material, compared with radically polymerizable ink.
Further, ink bags are required to have a light shielding property, because actinic radiation curable type ink is hardened by actinic radiation such as ultraviolet rays.
As a member having an ink resistance property and a light shielding property, there is considered an ink bag employing a metal such as SUS (Stainless Used Steel), which, however, is not practical because of its high cost. Further, depending on a polymerization type, there is sometimes an occasion where storage stability is affected by an amount of air in the ink bag to be deteriorated, as ink is consumed. For example, in the case of radically polymerizable ink, hydrolysis of acrylic ester representing main components is accelerated by moisture carried in from mixed air. Further, in the case of cationic polymerizable ink wherein an acid serves as active species, moisture in minute quantities contained in ink has a function to inhibit dark reaction, mixture of dried air causes a dehydration phenomenon, and dark reaction by an acid component generated slightly is accelerated.
To eliminate an influence of mixed air, a flexible packing material by which a volume of an ink bag can decrease as ink is consumed is appropriate. A specific ink bag is one which employs a sheet in which a flexible film-shaped light shielding member and an ink resistance member are combined, and is packing-heat-sealed while it is decompressed when ink is loaded. By using the flexible packing material, various functions can be offered, cost of an ink bag can be reduced, and waste matters can be reduced.
Therefore, an ink bag made of flexible packing material employing a multilayer laminated film composed of light shielding member of metal film having great light shielding property and of an ink resistance member, was studied, but it was impossible to give sufficient storage stability and durability to the ink bag, under such simple combination.
An ink bag manufactured is housed in an outer box under the condition that the ink bag is supported on a supporter, an ink outlet portion of the ink bag is fixed by the supporter and by the side wall of the outer box and a width of the ink bag is regulated by side walls of the supporter. Therefore, when the ink bag is moved in the course of transportation or of handling, or is vibrated, an ink storage portion of the ink bag is moved back and forth. When the ink storage portion is moved toward the ink outlet portion side, in particular, creases tend to be generated on the ink storage portion, because the ink storage portion results in the state of shrinkage.
After creases are generated once, the creases are easily generated on the same location repeatedly, to be rubbed by the inside wall of the outer box, thereby, pinholes tend to be generated on the location where creases have been generated. When the ink storage portion is made of a multilayer film having therein an aluminum foil layer, in particular, there has been a problem that the multilayer film is easily bent, and its bent portion is rubbed with the inside wall of the outer box to generate a pinhole that lowers light shielding property.
With respect to the light shielding property, Patent Document 1 discloses a proposal wherein a film that attenuates ultraviolet rays is brought into close contact with an ink tank that transmits ultraviolet rays, and the light shielding property and visibility of an amount of residual ink are taken into consideration. However, for the long term storage, this proposal is insufficient because it still has permeability for ultraviolet rays, although a level of the permeability is extremely low.
What is disclosed in Patent Document 2 is one having objects for obtaining mechanical strength of an ink tank member and for restraining an influence of extraction from the ink tank member on the ink. However, it is insufficient for satisfying low cost, light shielding property and ink resistance property. In the case of long term storage or of storage at high temperature, in particular, ink slightly arrives at a light shielding member, and causes a problem of deterioration of a light shielding member and of a decline of adhesion strength between the light shielding member and an ink resistance member.
(Patent Document 1) Japanese Patent O.P.I. Publication No. 2003-182111
(Patent Document 2) Japanese Patent O.P.I. Publication No. 2004-188903